The present invention relates to generally a collision detection device used for actuating a safety device for protecting a driver and passengers of an automobile vehicle in case of a collision, and more particularly a collision detection device which is actuated under an acceleration or deceleration only in a predetermined angle including the direction of the movement of the vehicle.
In the prior art collision detection devices, the deflection of a mass or weight for closing or opening the contacts under an acceleration or deceleration which a vehicle undergoes in case of a collision is limited to one direction so that there is a fear that the collision detection device is not actuated unless the direction of a collision coincides with the direction of the deflection of the mass or weight. In the United States it is required to protect the driver and passengers against the collision within .+-. 30.degree. relative to the direction of the movement of the vehicle so that there have been devised and demonstrated the collision detection devices in which the mass or weight can be deflected within a predetermined angle including the direction of the movement of the vehicle. In the collision detection devices of the type described, a plurality of contacts are disposed and spaced apart by the same distance from the rest position of the mass or weight within an angle through which is permitted the deflection of the mass or weight. However, in case of a collision, a vehicle undergoes not only the acceleration or deceleration in the direction of the collision but also the acceleration or deceleration in the lateral direction. Consequently, the mass or weight is deflected not in the direction of the collision but in the direction or sense of the composed acceleration at a speed in proportion to the magnitude of the composed acceleration. Therefore when the spacing between the contacts and the mass is short as with the case of the collision detection device for a compact car, the time period during which the mass or weight is kept in contact with the contact is short. That is, the actuation level is low. As a result, the safety device is actuated even in case of such a small accident as not to require to actuate the safety device.
In view of the above, the present invention has for its object to provide a collision detection device in which a contact spring which is interposed between two electrically isolated fixed contacts for closing them in case of an accident or collision is permitted to be deflected only in one direction regardless of the direction of the deflection of the mass or weight so that the level at which a collision is detected may be stabilized.